Accelerated apoptosis in the Timp-3–deficient mammary gland
Jimmie E. Fata, … , Roger A. Moorehead, Rama Khokha
Jimmie E. Fata, … , Roger A. Moorehead, Rama Khokha
Published September 15, 2001
Citation Information: J Clin Invest. 2001;108(6):831-841. https://doi.org/10.1172/JCI13171.
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Article

Accelerated apoptosis in the Timp-3–deficient mammary gland

Abstract

The proapoptotic proteinase inhibitor TIMP-3 is the only molecule of this family thought to influence cell death. We examined epithelial apoptosis in TIMP-3–deficient mice during mammary gland involution. Lactation was not affected by the absence of TIMP-3, but glandular function, as measured by gland-to-body weight ratio and production of β-casein, was suppressed earlier during post-lactational involution than in controls. Histological examination revealed accelerated lumen collapse, alveolar-epithelial loss, and adipose reconstitution in Timp-3–/– females. Epithelial apoptosis peaked on the first day of involution in Timp-3–null glands but at day 3 in wild-type littermates. Unscheduled activation of gelatinase-A was evident by zymography and correlated with earlier fragmentation of fibronectin in Timp-3–/– mammary. To obtain independent evidence of the proapoptotic effects of TIMP-3 deficiency, we introduced recombinant TIMP-3–releasing pellets into regressing Timp-3–/– mammary tissue and showed that this treatment rescued lumen collapse and epithelial apoptosis. Ex vivo, involuting Timp-3–/– mammary tissue demonstrated accelerated epithelial apoptosis that could be reduced by metalloproteinase inhibition. The physiological relevance of TIMP-3 became apparent as Timp-3–/– dams failed to reestablish lactation after brief cessation of suckling. Thus, TIMP-3 is a critical epithelial survival factor during mammary gland involution.

Authors

Jimmie E. Fata, Kevin J. Leco, Evelyn B. Voura, Hoi-Ying E. Yu, Paul Waterhouse, Gillian Murphy, Roger A. Moorehead, Rama Khokha

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Figure 1

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Early loss of milk secretion and β-casein expression in Timp-3–null mamm...
Early loss of milk secretion and β-casein expression in Timp-3–null mammary glands during involution. (a) Upon initiation of involution, the mammary gland to body weight ratio increased in wild-type (WT) mice but not in Timp-3–null mice. Significant differences were found at 2di. *P < 0.05. No differences were found thereafter. All time points were derived from at least n = 2 mice per genotype and are shown as mean ± SEM. (b) β-Casein protein declined rapidly after 1di in Timp-3–null mice compared with its gradual loss in wild-type mice. Immunoblot is representative of two separate experiments. Equal loading was confirmed by staining the membrane with Amido Black.